Fla. dolphins harbor potentially deadly bacteria

Feb. 8, 2014
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The researchers found 43 of 126 dolphins they tested had antibodies indicating exposure to the Chlamydiaceae bacteria, which can make them more vulnerable to other deadly infections. / Florida Today file photo

by Jim Waymer, Florida Today

by Jim Waymer, Florida Today

MELBOURNE, Fla. -- One in every three bottlenose dolphin tested in the Indian River Lagoon on Florida's Atlantic coast has antibodies to a bacteria that can make them more vulnerable to other deadly infections, according to a new study.

The finding comes as researchers struggle to figure out what has caused a rash of unexplained dolphin deaths in the lagoon.

"This is just one additional level of evidence that's concerning," said Greg Bossart, a marine mammal pathologist at the Georgia Aquarium and lead author of the study. "It starts to shed light on what's happening in the lagoon."

Researchers found 43 of 126 dolphins tested had antibodies indicating exposure to the Chlamydiaceae bacteria, which can make them more vulnerable to other deadly infections.

Bossart has been leading a federal study of lagoon dolphins' health since 2003.

This study, which involved 10 researchers, was published this month in the journal Diseases of Aquatic Organisms.

The researchers say the Chlamydiaceae bacteria could be one piece of the puzzle helping to explain why so many dolphins are dying here. At least 76 bottlenose dolphins died in the lagoon last year of a mysterious affliction that federal scientists are investigating.

Scientists don't know whether the bacteria also infects and harms manatees, which also have died in large numbers in the lagoon during the past year. At least 117 manatees died for reasons that federal biologists are trying to figure out.

While the lagoon dolphins don't show clinical signs of disease from Chlamydiaceae infection, the bacteria's presence could lower their immunity to other diseases, the researchers say.

The bacteria might also be affecting dolphin fertility, the researchers say, because in other species the pathogen causes reproductive disease and abortion.

Dolphins are considered sentinel species that can herald health threats to humans, biologists say. The same family of bacteria found in the dolphins can cause disease in humans.

"This can be a human disease, absolutely," Bossart said. "We don't know if it's due to the one that causes human disease or not."

"It may or may not be sexually transmitting," Bossart said. "We don't know. This is brand new data," he added. "It has been reported in some other marine mammals." Those include sea lions and monk seals.

The droppings of resident and migratory birds might be the main source.

"The reservoir for this disease can be birds," Bossart said. "This particular organism is found in seabirds."

For the past decade, Bossart and about 40 other scientists have examined and released more than 240 bottlenose dolphins, most of them from the Indian River Lagoon.

They have found antibiotic-resistant bacteria, a high incidence of tumors, heart problems, cancers, stomach ulcers, skin lesions, genital herpes and other ailments previously thought rare in dolphins. As many as half the dolphins studied in the lagoon so far suffer from some form of chronic infectious disease, suggesting compromised immune systems.

Dolphins captured near Merritt Island, especially, seem in poor health. And the researchers point to water tainted by partially treated sewage and runoff as the possible cause.

A study published in 2009 found 23 percent of the lagoon's bottlenose tested had triclosan - a common ingredient in antibacterial soaps, deodorants, toothpastes, shaving cream and mouthwash - in their blood.

"All these diseases, either directly or indirectly, resulted in immune system dysfunction," Bossart said. "It opens them up for other disease issues. That may explain why this area has such a high unusual mortality."

Scientists suspect a measles-like virus, called morbillivirus, has killed hundreds of bottlenose dolphins from New York to Virginia last year. The same pathogen hammered the bottlenose dolphin population from New Jersey to Central Florida in the late 1980s.

In July and August, more than nine times the historical average of bottlenose dolphins died or stranded in the mid-Atlantic region.